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Why to use Load Balancer with Floating IP?

Posted December 19, 2015 8.5k views
Server OptimizationLoad BalancingHigh Availability

I can notice every tutorial for using Floating IP is explained through this schematic:
https://assets.digitalocean.com/articles/high_availability/ha-diagram-animated.gif

I’m trying to understand why we need to use Load Balancers in combination with Floating IP ? Why not to use only pool of App servers with Floating IP (without Load Banalcers) ? When some server is down, the floating IP will be assigned to other server from the pool and the application will be still available.

Thanks

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nozomk
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2 comments
  • no1youknowz December 20, 2015
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    I have this very same question as well. I don’t understand the need for servers with HA Proxy installed. What if your app servers have a higher bw than the smaller low end servers with HA Proxy? The HA servers would reach their limit of bw faster.

  • COOBERS December 21, 2015
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    Without Load Balancers, you cannot use multiple App servers.
    Floating IP is not a dynamic switch mechanism (aka load balancer), instead it resolves biggest problem Digital Ocean had - lack of ability to have static yet dynamic IP’s in DNS settings.
    With it you don’t need services like CloudFlare to manage DNS.

    Unfortunately, there’s a catch. One droplet can support just one Floating IP. It means you cannot replace broken server with other LB server assigned to other Floating IP. It means only way to have proper redundancy is to have idle spare Droplets . If you will use 3 Floating IP’s you need to have 3 LB servers + at least one spare.

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rrojasa May 31, 2016

I want to implement redundant HA Proxy for Mysql Master/master configuration. As far as I know Floating IP are public, is there any way to get a private floating IP ?. For security and performance reason I don’t think that using public IP for HA Proxy in this Scenario (webservers communicating internally with database servers). Do you know any solution for this?

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  • thomasleerab60d April 23, 2017

    I am interested to know too! @rrojasa have you figure this part out?

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    • rrojasa June 9, 2017

      Hi,

      Not resolved the issue yet. I also created a DOLoad Balancer and applied DO Firewall rules to my backend DB servers. Firewall works on top of droplets but DO Load Balancer can’t be protected behind the DO Firewall , so Mysql Port is open to the internet.

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